31 aug 2018 kl. 21:38 skrev Ulf Volmer <u.volmer at u-v.de>: > On 31.08.2018 21:31, Michael Schumacher wrote: > >> certbot works only with ports 80 or 443? Can lego work with with IMAP >> ports like 143 or 993? The documentation is not very clear. > > basically - independent of the client - letsencrypt will only support > http/https or dns based challenges. > > so - if you want to get certificates for an imap only server, you will > have to setup an webserver for the challenge. or deal with your dns server. Setting up a web server is not needed - all you need is lego (which by the way is one statically linked binary since it's written in Go). If you use the HTTP challenge, lego will temporarily, only for the time needed to fulfill the challenge, listen for HTTP on the relevant port. In summary, lego contains a web server for the HTTP challenge.